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I want to recreate the following:

enter image description here

What I have is this:

\begin{equation} \label{eq1}
\begin{split}
\nabla f(x_i) = \nabla f(x_i, y_j, z_k) & \approx ( \dfrac{1}{2} \left( f(x_{i+1}, y_j, z_k) - f(x_{i-1}, y_j, z_k) \right), \\
 & \phantom{abc} \dfrac{1}{2} \left( f(x_{i}, y_{j+1}, z_k) - f(x_{i}, y_{j-1}, z_k) \right), \\
  & \phantom{abc} \dfrac{1}{2} \left( f(x_{i}, y_j, z_{k+1}) - f(x_{i}, y_j, z_{k-1}) \right) )
\end{split}
\end{equation}

Which produces this:

enter image description here

When I try to change the size of the first and last bracket with \left and \right I get an error. How else could I adjust the sizes of the first and last bracket?

PlsWork
  • 157
  • 3
    \left( ... \right) doesn't work over ampersands and multi lines equations. instead it you need to use \bigl( or \biggl( etc braces, or closed each line with \right. however, this not guaranty that the left and right parenthesis will have the same size. – Zarko Dec 06 '17 at 15:39

1 Answers1

3

Use \right. and \left.. LaTeX only processes the \lefts and \rights in a given equation line. That is, you need to have as many \lefts as \rights per line. In this sense, LaTeX is very different from the parliaments of this planet. 

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation} \label{eq1}
\begin{split}
\nabla f(x_i) = \nabla f(x_i, y_j, z_k) & \approx \left( \dfrac{1}{2} \left( f(x_{i+1}, y_j, z_k) - f(x_{i-1}, y_j, z_k) \right)
\right., \\
 & \phantom{abc} \dfrac{1}{2} \left( f(x_{i}, y_{j+1}, z_k) - f(x_{i}, y_{j-1}, z_k) \right), \\
  & \phantom{abc}\left. \dfrac{1}{2} \left( f(x_{i}, y_j, z_{k+1}) - f(x_{i},
  y_j, z_{k-1}) \right) \right)
\end{split}
\end{equation}
\end{document}